It has long been known that the “Flashing Light Effect” in Photosynthesis can enhance the light utilization efficiency leading to better productivity. The goal is to apply a photon flux density that is just enough to excite the majority of the light harvesting complexes to attain the maximum rate of growth, while simultaneously minimizing trapped surplus light, which renders losses in the form of heat and fluorescence. The excess absorbed light energy can cause damage to the photosynthetic apparatus from the reactive free oxygen radicals generated, known as photoinhibition. Thus, by using intermittent light, the number of excitations arriving at a closed reaction center decreases when flashes are shortened, permitting more efficient usage of light and less photodamage repair. The major potential boosts in bioproductivity stems from improving flux tolerance rather than from augmenting intrinsic photosynthesis efficiency. The ultimate rate limiting process for improving photonic flux tolerance and thus bioproductivity is the time scale for the dark reactions in algal photosynthesis. The matching of pulse duration, color spectrum, and instantaneous light intensity of the LED light output to the chlorophyll absorption, and subsequent dark reaction kinetics are the key to realizing superior flux tolerance.
Photosynthetic organisms use various pigments to absorb and convert light energy into chemical energy through photosynthesis. These pigments have specific wavelengths of light that are most strongly absorbed, with chlorophyll being the dominant and most important pigment for photosynthesis. Using colors of light that match the absorption of pigments in a particular organism has been shown to be more effective for driving photosynthesis over using full spectrum or weakly absorbed colors. However, as pigment densities increase, such as in the case of high density algal cultures, strongly absorbed wavelengths of light, such as blue and red, become very strongly absorbed at the surface of the culture and less light is allowed to penetrate deep into the culture. The most popular physical observable used to assess photosynthetic function and its subsequent down regulation in excess-light conditions is chlorophyll (Chl) fluorescence, because it is sensitive to a wide range of changes in the overall apparatus. Despite decades of research on the flashing light effect, there have not been any studies on the apparent increase in photon utilization efficiency (yield) or a minimization of non-photochemical quenching (NPQ), or heat dissipation using PAM Fluorometry. Thus, a need exists to address these deficiencies.